Hawaii Extended Forecast Discussion NWS Weather Prediction Center College Park MD 221 AM EDT Fri Apr 03 2020 Valid 00Z Sat Apr 04 2020 - 00Z Sat Apr 11 2020 ...Locally heavy rain possible next week... A deep upper-level low initially centered near 35N Friday morning is forecast to remain relatively stationary into the weekend, before beginning a gradual northeastward movement Sun-Mon as it weakens and interacts with a shortwave crossing the North Pacific. At larger scales, model/ensemble consensus is relatively good for this system. Where solutions continue to differ is on the magnitude of moisture return ahead of it, and on the potential for any heavy rainfall as the associated slow-moving cold front crosses Hawaii. With 500 hPa heights within the upper low at least 4 standard deviations below average Fri-Sat, the potential for significant northward moisture transport east/southeast of the low center is certainty there. Guidance generally shows agreement that the upper low should become gradually less anomalous through time as it moves east/northeast, however. The ECMWF and GFS both maximize PWs in the 1.5-1.7 inch range along the slow-moving or possibly stalled front across Hawaii next week. Low-level flow in the vicinity of the front looks relatively weak, however, which may serve to limit areal coverage of heavier rains. ECENS ensemble precipitation probabilities show some modest signal for locally heavy rains, primarily across the western/central Hawaiian islands during the early to middle portion of next week. The GEFS was even less enthusiastic. Nonetheless, given relatively good moisture and the strong nature of the upper low north of the state, would expect the potential for at least locally heavy rains next week. The ECMWF and GFS differ by late next week on whether the front moves east of the state (GFS), or whether it lingers across Hawaii as it gradually washes out. A look at ensemble means suggests the latter scenario may be more likely, which would keep the potential for at least scattered convection with locally heavy rains a possibility across Hawaii through late next week. Ryan